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Discussion Starter #1 (Edited)
Hello everyone! It's a bit of a ramble but please give it a read and help me, if possible!

I drive an '03 Ford Focus wagon with the 2.0 Zetec. It has been quite trouble free with mostly routine maintenance for the last few years. However since last December, I have been experiencing these weird episodes of the car threatening to overheat, especially in extended traffic jams(doesn't usually matter the time, though middays are particularly troublesome). However, the car's temp will stabilize as soon as I turn on the air conditioning.

I first traced the problem to a dodgy primary cooling fan. I changed the fan, and the problem seemed to go away, temporarily.

It was then apparent that my coolant overflow tank had a crack in it. It wasn't too big, but then I believed it would be enough to mess up the pressure of my cooling system. I then sought another expansion tank from my mechanic.

After searching for an extended period however, he could not find the exact type of overflow tank.(I happen to be in Ghana, Foci are not too common here)[hihi] He however found a smaller one that fit quite well. The problem however, never really went away- although it got a bit better.

Things however came to a head last week as my temperature needle quickly charged almost to the red on my way to work. I pulled over, and whiles the coolant hadn't boiled, the hose leading to my thermostat housing had expanded to more than twice its size. Seeing that, I concluded I had a failed thermostat and quickly removed the thermostat on the side of the road. I made it to work with no problem.

I automatically assumed my thermostat had failed closed, thus solving my mystery. Boy, was I wrong.

Three days later in extreme rush hour traffic, I caught the temp needle inching away from it's normal midpoint to the red...I quickly turned on the air conditioning and the needle quickly fled back to its point at the center. Sigh. The problem was back! When I got home and checked, the pipe leading to the thermostat housing had expanded once again.

I have multiple suspicions, highest of which is the smaller overflow tank. I believe it affected the pressure of the entire cooling system. Here are pictures of the old and new tanks so y'alls can be the judge.


But then, could it also be that my head gasket is going? I haven't really given this much of thought as the signs (oil in coolant/ vice versa,) are not noticable. However I do have to top up coolant every week or so (Have had long standing thermostat housing leak as well).

Thanks for reading this far and not clicking away in boredom . Please help a brother!

Cheers!
 

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Discussion Starter #3
If the temperature goes down with the air conditioning on its your cooling fan. The reason why your temp is going down when you turn on the air-conditioning is because it's turning on the fan. It's more likely the fan resistor.

https://www.rockauto.com/en/catalog/ford,2003,focus,2.0l+l4+dohc,1431898,cooling+system,radiator+fan+resistor,11556

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Thanks for the prompt reply!

I did change my entire fan assembly, including the resistor, One of the fans always comes on when the temparature is optimal, but come to think of it, the second fan never comes on, unless I switch on the airconditioning. Is this usual?

Also, the former fan is at full blast when the needle starts crawling to the red.
 

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Hello,
I have an 02 wagon with the Zetec. When the vehicle does not have the AC on the cooling fans are commanded on/off by the PCM mainly by the input from the cylinder head temperature sensor (CHTS) which is located in the cylinder head near the alternator. They do fail and when they do the typical system response is erratic or no cooling fan operation. The sensor is a huge PITA the change (alternator has to be partially removed) so I would try to test it first. Im not sure what the resistance is supposed to be at various temps.

Good luck
Paul
 

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i have had to do 3 repairs for overheating on a 2000 2.0L zetec, mind you I have had the car since 70k, it has over 120k now. first it was the radiator so i changed that, then the thermostat, i had to replace the whole assembly because it had a crack in it, the actual thermostat was good but i threw in the new one anyways. the last repair was the fan assembly because the resistor on the old fan had gone bad. i checked the fuses for the fans and they were all good, the relays too.. so i got a new fan assembly and all is like new now. hope this helps!
 

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Discussion Starter #6 (Edited)
Hello,
I have an 02 wagon with the Zetec. When the vehicle does not have the AC on the cooling fans are commanded on/off by the PCM mainly by the input from the cylinder head temperature sensor (CHTS) which is located in the cylinder head near the alternator. They do fail and when they do the typical system response is erratic or no cooling fan operation. The sensor is a huge PITA the change (alternator has to be partially removed) so I would try to test it first. Im not sure what the resistance is supposed to be at various temps.

Good luck
Paul
Thank you! I guess I'll quickly look them up, (and put my findings here). It seems my fans work quite oddly then...darnit
 

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Discussion Starter #7
i have had to do 3 repairs for overheating on a 2000 2.0L zetec, mind you I have had the car since 70k, it has over 120k now. first it was the radiator so i changed that, then the thermostat, i had to replace the whole assembly because it had a crack in it, the actual thermostat was good but i threw in the new one anyways. the last repair was the fan assembly because the resistor on the old fan had gone bad. i checked the fuses for the fans and they were all good, the relays too.. so i got a new fan assembly and all is like new now. hope this helps!
I have actually gone ahead to order a new thermostat housing, as well as thermostat...since I'm in Africa, they'll take a couple of months to get here. (Sigh!)

After reading this, I decided to have a really good look at my radiator; it has definitely seem better days- I will definitely have to get a new one.

Thanks for the help!
 

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I have actually gone ahead to order a new thermostat housing, as well as thermostat...since I'm in Africa, they'll take a couple of months to get here. (Sigh!)

After reading this, I decided to have a really good look at my radiator; it has definitely seem better days- I will definitely have to get a new one.

Thanks for the help!
Since you car cools normally when the fans run - when commanded by the AC - then there is nothing wrong with your thermostat/housing, fans, radiator, etc. You can replace them all if you want but that is not the core of your issue.

Paul
 
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I have actually gone ahead to order a new thermostat housing, as well as thermostat...since I'm in Africa, they'll take a couple of months to get here. (Sigh!)

After reading this, I decided to have a really good look at my radiator; it has definitely seem better days- I will definitely have to get a new one.

Thanks for the help!
You can bypass the resistor to force both fans on. Also swap out the fan relay.
Mine had a false overheat...turned out $27 CHT fixed it.

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I actually just had the same issue happen to me for the second time. I have a 2002 Focus SE 2.0l Zetec. I have replaced the thermostat, thermostat housing, and the fan resistor. One of the ports on the resistor was burnt, so I hoped that was THE issue rather than AN issue. Everything was fine for 8 months, then it started overheating again last week in stop/go traffic. The first thing I checked was resistor and sure enough, it was burnt out again! I ordered a new one immediately, then proceeded to check the fuses because it hadn't even lasted a full year. All of the fuses were fine, the thermostat was good, coolant was flowing through the radiator just fine. I've had the new resistor installed for a few days now and I can hear the fan kick on without having to blast the A/C! Hopefully all stays well and I won't have to spend another $40 on the same part! If anyone has any other suggestions for future situations, please share!
 

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Discussion Starter #11
Man, I know this is a bit long in coming but it might help those who have my exact problem (though very unlikely). As it turned out, 1)my CHT sensor was on its way out and 2) my fans were rewired to start up with the car! (a very common practice by mechanics over here). It seems they kind of rewired it for only the first(slower) fan to come on. I guess I will figure that out after tackling my CHT issue, which has become a big PITA. Thanks y'alls!
 

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According to my understanding, the part in question is a thermal fuse. What I dont understand is why this is necessary. Was a thermal fuse used to protect the resistors? And if so then why because the entire assembly gets replaced, whenever this happens rather than just the fuse. I am considering ordering 10A thermal fuses from Digi-Key, but perhaps with a higher temperature rating or just eliminating the fuse altogether.
 
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